Right to left shunts- BLUE

Question 1

Right to left shunts (blue babies!)

List types and common presenting features

Answer 1

• Present with cyanosis (O2 sats = 94%), usually in first week of life
• Tetralogy of Fallot
• Transoposition of great arteries

Question 2

List the key features of tetralogy of fallot

Answer 2

Clinical features

• Large VSD
• Overiding aorta- w/ respect to ventricular septum
• Subpulmonary stenosis- right ventricular outflow tract obstruction
• Right ventricular hypertrophy (result of PS)

Symptoms

• diagnsed antenatally
• severe cyanosis in first few days of life
• cyanotic/ hypercapnic spells on squatting exercise in late infancy (less common in developed world)
• NB episode of cyanosis/hypercapnia: increasing cyanosis, irritability or inconsoable crying (severe hypoxia), breathlessness, pallor (tissue acidosos)

Signs

• murmur first few months of life
• clubbing of fingers/ toes- older children
• loud harsh ejection systolic murmur at left sternal edge from day 1 of life

Question 3

Early and late management of TOF

Answer 3

• Early
  
  • ​shunt to increase pulmonary blood flow
  • surgical placement of artificial tube between SCA and pulmonary artery ‘Blalock-Taussig’ shunt or balloon dilatation of right ventricular outflow tract
• Late
  
  • ​surgery- closing the VSD, relieving right ventricular outflow tract obstruction (artificial patch extending across pulmonary valve)
• Acute management of cyanotic spell
  
  • ​<15 min self limiting and followed by period of sleep
  • > 15min sedation/ pain relief (morphine), IV propanolol/ a-adrenoceptor agonist (peripheral vasoconstriction), IV fluids, HCO3 to correct acidosis. muscle paralysis and artificial ventilation in order to reduce metabolic oxygen demand

Question 4

Understand the parallel circulation and duct dependence in TGA

Answer 4

• Aorta–> right ventricle
• Pulmonary artery–> left ventricle
• Deoxygenated blood pumped straight back to the systemic circulation
• Oxygenated blood pumped straight back to the lungs
• Unless mixing of blood occurs i.e. w/ VSD, ASD, PDA or therapeutic intervntions this condition is not compatible with life
• Presentation: cyanosis (maybe profound and life-threatening), usually on day 2 of life- closure of DA, +/- loud, single second heart sound, +/- systolic murmur

Question 5

Recognise the urgent need to atrial septiotomy and later arterial switch in TGA

Answer 5

• Maintain patency of DA with prostagladin infusion
• Ballon atrial septiotomy
  
  • ​ballon passed through umbilical or femoral vein –> right atrium –> foreman ovale
  • ballon inflated in left atrium
  • pulled back through atrial septum–> tears–> formen ovale incompetent
  • mixing of systemic and pulmonary venous blood within the atrium- MIXING ESTABLISHED
• Arterial switch
  
  • ​neonatal period (usually first few days of life)
  • PA and aorta transected ABOVE arterial valves
  • switched over
  • coronary rtery trasfer to new aorta